While fucking a girl doggystyle, preferably, in the ass, you thrust extra hard making her moan in pain/pleasure, you then shit in your hand and slam dunk it in her open mouth.

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.